Power transmission



June 3, 1941- F. T. HARRINGTON POWER TRANSMISSION Filed Nov. 7, 1938 INVENTOR FERRIS T HARRINGTON BY 1 W ATTORNEY Patented June 3, 1941 POWER TRANSMISSION Ferris T. Harrington, Detroit, Mich, assignmto Vickers Incorporated, Detroit, Mich., a corporation of Michigan Application November 7, 1938, Serial No. 239,308

4 Claims.

This invention relates to power transmissions, particularly to those of the type comprising two or more fluid pressure energy translating devices one of which may function as a pump and another as a fluid motor.

The invention more particularly relates to spot welders wherein a transmission of this type may be used to automatically feed the work and perform the welding operations thereon.

An object of this invention is to provide means for causing the welding operations to occur at equal intervals on a work piece and means for feeding the work in one direction for a predetermined distance after each welding operation to position it for the next operation.

Another object is to use the return stroke of the work feeding mechanism to feed another piece of work to be welded.

Still another object is to provide means for automatically stopping the machine after a piece of work has been finished and a means for stopping the machine in an emergency.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred form of the present invention is clearly shown.

In the drawing:

The single figure is a diagrammatic view of a hydraulic power transmission incorporating the preferred form of the present invention.

A pump I and a pump I2, both of which may be of the fixed displacement type and driven by a prime mover such as an electric motor not shown, have suction conduits I4 and I6 respectively through which fluid may be withdrawn from a tank I8 and delivery conduits 20 and 22. The conduit 20 extends to a relief valve 24 which is adapted to bypass fluid from the conduit 20 to the tank through a conduit 26 and a conduit 28 whenever a predetermined safe pressure is exceeded in the conduit 20. From valve 24 conduit 20 extends to the pressure port of a pilot-operated four-way valve 30. The valve 80 has cylinder ports 32 and 34 which are connected by conduits 86 and 88 to the head ends of cylinders 40 and 42 respectively. A piston 44 in cylinder 40 and a piston 46 in cylinder 42 are both rigidly mounted on a piston rod 48. The rod 48 may be connected to operate a reciprocating work carrier to shift the work into various positions with respect to the tools carried by the piston rods I08 and H0. The four-way valve 80 also has ports 50 which are connected by a conduit 52 to a port 54 .of a pilot-operated six-way valve 66. A port 58 of valve 56 is connected to the pressure line 20 by a conduit 60. The valve 68 has ports 62 and 64 which are connected by conduits 66 and 68 respectively to the opposite ends of a volumetric displacement metering cylinder late the effective stroke of the piston 12.

10. A piston 12 is slidably mounted in cylinder 10. An adjustable stop 14 is provided to regu- The valve 56 also has ports 16 which are connected to the tank by a conduit 18.

The delivery conduit 22 of pump I2 extends to a relief valve 80 which is connected to the tank by a conduit 82 and conduit 28. From valve 80 the conduit 22 extends to the pressure port of a pilot-operated four-way valve 84. Valve 84 has cylinder ports 86 and 88 and tank ports 90. Port 86 is connected by a conduit 92 to a conduit 84 which opens to the head ends of two cylinders 96 and 98. Port 88 is connected by a conduit I00 to a conduit I02 which opens to the rod ends of the two cylinders 96 and 88. Slidably mounted in cylinders 96 and 98' are pistons I04 and I06 mounted on piston rods I08 and H0 respectively and adapted to carry the usual welding electrodes or tools; A rack and pinion mechanism H2 is employed to maintain pistons I04 and I06 constantly in step. The tank ports 80 of valve 84 are connected to the tank by conduit 28.

A pilot valve I I4 has a valve member I I6 whose position is controlled by a hand lever I I8. Valve I I4 has a pressure port P, a tank port T and delivery ports I and 2. The port P is connected to the pressure conduit 20 by a conduit I20. The port T is connected to the conduit 52 by a conduit I22. A conduit I24 extends from port I of valve II 4 to the left-hand pilot connection of the valve 30. The conduit I24 also extends to a port I of a pilot valve I26 which has a valve member I28. Dogs I30 and I32 carried on rod 48 are adapted to engage the arms I36 and I38 of valve I26 respectively. The arms I86 and I38 control the position of the valve member I28. The port 2 of valve H4 is connected by a conduit I40 to the right-hand pilot connection of valve 30. The conduit I40 also extends to a port 2 f the valve I26.

Valve I26 has ports P and T respectively connected by conduits I42 and I44 to the upper and lower pilot connections of a pilot-operated fourway valve I46. The valve I46 has ports I48 which are connected to the pressure conduit 28 by a conduit I50. A port I52 of valve I46 is connected by a conduit I54 to the right-hand pilot connection of valve 84 and a port I56 of valve I46 is connected to the right-hand pilot connection of valve 66 by a conduit I58.

A conduit I connects the pressure conduit 20 to the pressure port of a pilot-operated fourway valve I62. The valve I62 also has ports I64, I66 and I68. The port I64 connects by means of a conduitv I10 to the left-hand pilot connection of valve 56. A conduit I12 extends from conduit I10 to the left-hand pilot connection of valve 84. A conduit I14 extends from port I66 of valve I62 to one of the ports of a solenoid-operated two-way valve I18, the spool of which is normally held in its right-hand position by a spring I18. Another port of valve I18 is connected by a conduit I88 to the conduit I88. The ports I68 of valve I62 are connected to the tank conduit 28 by a conduit I82.

A conduit I84 extends from conduit 82 to a port I86 of a bypass valve I88. The spool I88 of valve I88 is normally held in.- its right-hand position by a spring I82. A passage I84 connects the port I 86 to the opposite ends of the bore of spool I88. Due to the diflerential area at the two ends of spool I88 the pressure in conduit I84 is effective to react against spring I82 and open the valve when a predetermined pressure is reached in conduit I84. A check valve I98 permits free flow from a port 288 to the port I86. The port 288 is connected by a conduit 282 to the upper pilot connection of valve I62.

A conduit 284 extends from conduit I88 to a port 286 of a bypass valve 288 which is the same as valve I88 and has a spool 2I8 normally held to the right by a spring 2I2. A passage 2 connects the port 286 to the right and left ends of the bore of valve 288. A check valve 2I8 permits free flow from a. port 228 to port 288 of valve 288. Port 228 connects by a conduit 222 to the lower pilot connection of valve I62. A pressure responsive switch 224 having a piston 226 adapted to operate a two-circuit electric switch 228 is connected to conduit 82 by a conduit 238. A check valve 232 permits free flow of fluid from conduit 238 while a restricted passage 233 serves. to provide a dashpot action on the return movement.

An electrical conductor 234 extends through switch 228 to an electric control panel 236 to provide a circuit for controlling the current to perform welding operations. The control panel may be of any suitable type which is eifective to cause the welding current to flow for a predetermined interval after the controller is rendered effective by the closing of the circuit 234. The other circuit of switch 228 connects one side of the line L by means of a conductor 231 to the operating coil of a time delay relay 238 and then duit I88 when the spool is in its right-hand.

position, illustrated. Stops 246 and 248 in cylinders 48 and 42 respectively are provided to adjust the limits of travel of pistons 44 and 46 for different lengths of work that are to be welded.

Before describing the operation of the machine through a normal cycle, the at-rest conditlon of the circuit may be set forth as follows: With the parts in the positions shown in the drawing and the pumps I8 and I2 operating, fluid is drawn from. the tank I8 through conduit I4 by pump I8 and delivered through conduit 28 to the pressure port of four-way valve 38. Fluid passes through valve 38 and out of port 32 and by means of conduit 36 to the head end of cylinder 48. As the pistons 44 and 48 arein their extreme right hand limit 08 travel,

which is adjustable by stop 248, they do not ,I24 to the left hand pilot connection of valve also delivers fluid to port I of i 38. Conduit I24 valve I28 and out of port T to conduit I44 which directs the fluid to the lower pilot connection of four-way valve I48. Tlhe conduit I58 delivers pressure fluid from conduit 28 to the ports I48 of valve I46. As the spool of valve I46 is in its upper position, port I48 is connected to port I 52. Conduit I64 delivers fluid from port I82 to the right-hand pilot connection of four-way valve 84. Since both valves I46 and 84 are already in their upwardly and left-hand shifted positions, respectively, the only path of escape of the fluid delivered by pump I8 is to pass through the relief valve 24 through conduits 26 and 28 to the tank.

The pump I2 draws fluid from tank I8 through conduit I6 and delivers it through conduit 22 to the pressure port of valve 84. .The spool of valve 84 being in its left-hand position, conduit 22 is connected to the port 88. Accordingly fluid is delivered from conduit 22 to conduit I88 and through conduit I 82 to the rod ends of the cylinders 96 and 88, thereby causing the pistons I84 and I86 to remain in their upper position. The pistons I84 and I86 being stalled, pressure will build up in conduit I 88. -The pressure fluid in conduit I88 passes through conduit 284 to port 286 of valve 288. Passage 2 of valve 288 passes pressure fluid from port 288 to the right and left hand ends of spool 2I8 respectively, thereby moving the spool 2I8 to the left against the resistance of spring 2I2.

The ports 288 and 228 of valve connected, fluid is passed to the nection of valve I82 holding the spool of tion.

Pressure fluid passes from conduit 28 through conduit I68 to the pressure port of four-way valve I62. The port I84 now being in communication with the pressure port, fluid is delivered by conduit I18 to the left-hand pilot connection of valve 86 holding the spool of the latter in its right-hand position. The conduit I12 delivers fluid from conduit I18 to the left-hand pilot connection of valve 84. The spool of valve 84, however, does not move because an equal 288 now being lower pilot conby conduit 222, thereby valve I62 in its upper posipressure builds up to open relief valve 88 and bypass the pump delivery to' the tank through conduits 82 and 28.

From the foregoing it will be seen that the machine is at rest, with none of the pistons'or valves moving.

. In order to start a working cycle the valve member I I8 of pilot valve 4 is rotated clockwise by lever I I8 connecting port P to port 2. Pressure fluid in conduit 28 accordingly passes through conduit I 28, ports P'and 2 of valve II4,

head end of cylinder 46 passes through conduit 36, ports 32 and 50 of valve 30, conduit 52, ports 54 and 62 of valve 56, and conduit 66 to the left end of the metering cylinder 16. As the exhaust fluid from cylinder 40 enters cylinder 16 the piston 12 moves to the right until it comes up against stop 14. When the piston 12 stalls it blocks the exhaust fluid from cylinder 46. Therefore the distance of travel of the pistons 44 and 46 is determined by the travel of piston 12 which is'adjustable by stop 14. This movement of pistons 44 and 46 is only a fraction of their total possible travel permitted by the limit stops 246 and 246.

Fluid in the right end of cylinder passes to the tank through conduit 66, ports 64 and 16 of valve 56 and conduit 16. The same pressure fluid in conduit I40 that shifted valve 36 is delivered to port 2 of pilot valve I26 which directs the fluid from port P and through conduit I42 to the upper pilot connection of valve I46.

The spool of valve I46 accordingly shifts downwardly cutting off the pilot pressure that was holding the spool of valve 64 to the left and connecting port I52 to the tank through port I56, conduit I60, valve I16 and conduit 244. The

pilot pressure that is on the left hand pilot connection of valve 64, as previously described, now shifts the spool of valve 64 to the right, connecting its pressure port to port 86 and port 66 to r the tank port 66.

Pressure fluid in conduit 22 is now directed to port 66 of valve 64, through conduits 62 and 64 to the head ends of cylinders 66 and 66. The

pistons I64 and I06 move downwardly carrying rods I06 and H0 to perform a welding operation on the work which was fed into position by the movement of pistons 44 and 46. Exhaust fluid from the rod ends of cylinders 66 and 66 passes into conduit I02, conduit I00, ports 66 and 66 of valve 64, and conduit 26 to the tank. When the pistons I64 and I06 stall against the work, pressure will build up in conduit 62. Pressure fluid in conduit 62 passes through conduit I64 to the Pressure fluid in conduit 20 passes through conduit I to the pressure port of valve I62. The spool of valve I62 being down, the pressure portis connected to port I66 which delivers fluid through conduit I14 to valve I16 where it is blocked, for the time being.

At the same time that pressure increased in conduit I64 the same thing occurred in conduit 230. Pressure fluid in conduit 230 passes through the check valve 232 to move the piston 226 of solenoid 242, thence toline L The solenoid 242 moves the spool of valve I16 to the left against resistance offered by spring I16, connecting con- 7 duit I14 to conduit I66.

There being pressure fluid in conduit I14 as previously described, it now passes through valve I16, conduit I66 and conduit I56 to the righthand pilot connection of valve 56, the spool of which shifts to the left. 'The ports 56 and 64 of valye 56 now being connected, pressure fluid from conduit 20 passes through conduit 66, ports 56 and 64 and conduit 66 to the right end of metering cylinder 10. The piston 12 accordingly moves to the left to reset itself for the next advance of pistons 44 and 46. Fluid in the left end of cylinder 16 passes through conduit 66, ports 62 and 16 of valve 56 and conduit 16 to the tank.

Pressure fluid in conduit I56 is also directed to the port I56 of valve I46, the spool of which is in its down position, out port I52 and through conduit I54 to the right-hand pilot connection of valve 64 thereby shifting its spool to the left. Fluid from the left end of the valve 64 passes to the tank by conduit I12, conduit I10, ports I64 and I66 of valve I62, conduit I62 and conduit 26. The pressure port of valve 64 now being connected to port 66, pressure fluid is delivered from conduit 22 to conduit I00 and from there by conduit I62 to the rod ends of cylinders 66 and 66 causing the pistons I 04 and I66 to move upwardly and away from the work.

When the valve 64 was shifted to the left conduit 230 was opened to the tank through conduit 62, ports 66 and 66 of valve 64 and conduit 26 thereby opening switch 226 to shut ofl welding current and to break the circuit 231 of relay 236 which in turn deenergized solenoid 242 allowing valve I16 to return ,to its normal position as shown.

When the pistons I04 and I06 return to their uppermost position, pressure builds up in conduit I00 and is transmitted through conduit 204 to port 266 of valve 206. As previously described the pressure fluid in passage 2 shifts spool 2I6 to the left, opening port 206 to port 220. Fluid is delivered from port 220 and through conduit 222 to the lower pilot connection of valve I62, the

' spool of which is shifted upwardly. Fluid in the switch 224 to the right which closes the twocircuit switch 226. The circuit 234 is made, which extends to the electric panel 236, to initiate an impulse of welding current. The other circuit of switch 226 connects the line L by conductor an to the operating coil of time delay relay m,

I6 6 of valve I66, conduit I64, conduit 62, ports 66 and 66 of valve 64, and conduit 26.

Pressure fluid in conduit 20 is now delivered through condultl60, the pressure port of valve I62, port I64, and conduit I16 to the left-hand pilot connection of valve 56. Accordingly the spool of valve 56 shifts to the left.

Fluid in the right end of valve 56 passes to the tank by conduit I56, conduit I66, passage I11 of valve I16, and conduit 244.

The machine is now ready to automatically start another operation as has just been described. The metering cylinder 16 permits pistons 44 and 46 to advance another step to the left and the same cycle of operations is repeated.

This action will continue until piston 44 moves against stop 246.

As the piston 44 moves against stop 246, do I32, carried on rod 46, moves lever I36 to rotate valve member I26 of valve I26 in a counterclockwise direction. So with valve H4 in its clockwise position, the machine is stopped as will now be described.

Pressure fluid in conduit 20 passes through conduit I20, ports P and 2 of valve H4, and conduit I40 to hold the spool of valve 30 to the left. Conduit I40 also delivers fluid through ports 2 and T of valve I26, conduit I44 to the lower pilot connection of valve I46, shifting the same upward. Pressure fluid is then directed from conduit 20 through conduit I50, ports M6 and I52 of valve I46, and conduit I54 to the right-hand pilot connection of valve 84 thereby holding the spool of valve 84 to the left.

Therefore, with valves 30 and 84 in the positions just described, pressure fluid will be delivered to the head end of cylinder 42 and to the rod ends of cylinders 96 and 96. The machine is accordingly brought to rest with the pistons 44 and 46 at their extreme left limit of travel and pistons I04 and I06 in their uppermost positions.

In order to start another series of operations in the opposite direction the lever II8 of valve H4 is moved in a counter-clockwise direction connecting ports P to ,I. Pressure fluid is then delivered through conduit I24 to the left-hand pilot connection of valve 30, shifting its spool to the right. Accordingly fluid is delivered through conduit 36 to the head end of cylinder 40, causing pistons 44 and 46 to move to the right for a distance governed by metering cylinder I0. A similar cycle of operations will now take place, identical to that previously described except that pistons 44 and 46 are moving to the right in stepby-step fashion, between cycles of advance and return of the welding pistons I04 and I06.

An emergency stop is provided for stopping the machine while pistons 44 and 46 are between their limits of travel. Assuming that valves H6 and I26 are in their counter-clockwise position with the pistons 44 and 46 traveling to the right somewhere between their limits of travel and it is desired to stop the machine, the lever II8 of valve I I4 is moved in a clockwise direction. Presvalve I16 passing through conduit I80 is blocked,

from reaching the right-hand pilot connection of valve 84, at port I56 of valve I46.

As pressure fluid is being delivered through conduit 38 from valve 30, pistons 44 and 46 will now move to the left to the point where metering piston I2 abuts stop 14. Since pilot pressure to aae gooe adaptedto operate a spot welding machine the combination of a fluid motor for advancing and retracting a welding tool, a fluid motor for advancing a work carrier in forward and reverse dir ctions relative to the tool, pump means for supplying fluid to operate said motors, control means for causing repeated advance and return cycles of the tool operating motor, and control means including a volumetric displacement metering device for causing actuation of the work carrier motor in a step-by-step fashion and including means responsive to pressure built up at the end of a stroke of the tool operating motor for resetting said metering device.

2. In a hydraulic power transmission system adapted to operate a spot welding machine the combination of a fluid motor for advancing and retracting a welding tool, a fluid motor for advancing a work carrier in forward and reverse directions relative to the tool, pump means for sup plying fluidto operate said motors, control means for causing repeated advance and return cycles of the tool operating motor, control means including a volumetric displacement metering device for causing actuation of the work carrier motor in a step-by-step fashion, means responsive to travel of the work carrier motor through a predetermined distance for stopping further actuation of said motors, and means for reversing the direction of travel of the work carrier motor, said reversing means being interconnected with the stopping means to render the latter ineffective by shifting said reversing means.

3. In a hydraulic power transmission system adapted to operate a spot welding machine the combination of, a fluid motor for advancing and retracting a welding tool, a fluid motor for advancing a work carrier relative to the tool, pump means for supplying fluid to operate said motors, and electric controller for initiating and terminating the flow of welding current, control means for causing advancing and retracting strokes of the tool operating motor, said control means including pressure responsive means for initiating operation of the electric controller after a predetermined pressure is built up on the advancing stroke of the tool operating motor, pressure responsive time delay means for thereafter reversing the flow to the tool operating motor to initiate the retracting stroke, and means rendered operative by the tool operating motor for shift valve 84 and raise pistons I04 and I 06 is blocked at port I56 of valve I46, the pistons I04 and I06 will stop. Because the action of pistons I04 and I06 controls the movement of pistons 44 and 46, the latter will also stop.

As pistons 44 and 46 reach their extreme righthand position, dog I30 on rod 48 will move lever I36 to rotate valve member'I28 of valve I26 in a clockwise direction and stop the machine in the same manner as when it was traveling to the left.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is topbe understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimedis as follows:

1. In a hydraulic power transmission system controlling the flow to the work carrier motor to initiate an advancing stroke thereof.

4. In a hydraulic power transmission system adapted to operate a spot welding machine the combination of a fluid motor for advancing and retracting a welding tool, a fluid motor for advancing a work carrier in forward and reverse directions relative to the tool, pump means for supplying fluid to operate said motors, control means for causing repeated advance and return cycles of the tool operating motor, control means for causing said work carrier motor to advance step by step a predetermined distance in sequence 

